Electromagnetic oscillating pumps are well known in the art. Typically, an electromagnetic coil is utilized to move an armature carried by an impeller relative to the frame assembly of the pump. Upon energization, a bellows-shaped discharge end of the impeller, defining a discharge chamber, is compressed, thereby decreasing the volume of the discharge chamber. This decrease in volume forces the liquid inside the chamber out of the pump through a one-way discharge valve.
Upon de-energization, a spring or permanent magnet returns the impeller to its original position or beyond, thereby increasing the volume of the discharge chamber. As a result, a partial vacuum is created inside the discharge chamber, and liquid is drawn from an inlet end of the impeller, past a center valve, and into the discharge chamber. The electromagnetic coil is then re-energized and the cycle is repeated, thereby producing a stop-and-go flow in one direction. Oscillations on the order of 60 times per second, however, create a flow that is substantially continuous.
Currently, the oscillating pumps known in the art use fixed springs or a permanent magnet as the opposing force to the electromagnetic forces. McNaull U.S. Pat. No. 5,567,131, for example, discloses an electromagnetic oscillating pump using a spring biased valve and a return spring which is affixed between the armature and the base of the pump to retract the armature. At least one disadvantage to using fixed springs, however, is that each oscillation does not perfectly compress the springs along their axes, thereby increasing the wear and decreasing the life of the springs. In addition, potential spring misalignment may cause increased friction resulting in decreased pump efficiency.
The present invention is advantageous in that it utilizes springs whose ends are not fixed. As a result, the springs automatically adjust to minimize the non-axial forces on the springs, thereby increasing their useful life. Therefore, the need exists for an electromagnetic oscillating pump that has self-aligning springs to provide the return force for the armature.